crystal clear : was : RE: [sdiy] Simple discrete Unity-Gain Follower ?

[Magnus Danielson]

From: "Czech Martin" <Martin.Czech at Micronas.com>
Subject: RE: crystal clear : was : RE: [sdiy] Simple discrete Unity-Gain Follower ?
Date: Wed, 7 May 2003 16:23:39 +0200

> >just a messy legacy which is best forgotten. Passive crossovers is just where
> >you loose out before even turning the rig on. I don't like it in any speakers
> >actually. Active cross-overs and separate amplifiers is the natural choice here
> >to get any form of control.
> 
> What about passive crossovers in the higher frequency range, above 1kHz or so?
> I think the component values get smaller there, so it's easier to have inductance
> and capacitance without too much side effects? Most tweeters have a lot of damping built in. And a passive highpass will automatically protect tweeters from DC...

No, you really want to avoid that. You want the time compensation anyway, and
doing that in passive filters for large scale signals? No thanks. It all goes
into active filters where it is easy to make well matched and stable
electronics. Also, I want individual limiters and tossing such in as passive
components in effective means a non-linear device in there... naaa... active
cross-over filters it is.

Some may say that this is only large-system design rules, could you then
explain why my rather small Genelec speakers follow the same principles and do
a pretty good job (only good for home-sessions for Harrys little band).

Actually, I think you fool yourself on the simplicity of a common amplifier and
passive cross-over filters. You need a much bigger amplifier than if you had
two smaller amplifiers. The passive filter naturally needs to use components
that take much more power than an active counterpart. It is easier to make a
more complex filter in active electronics. Once you accepted the separate
amplifiers (which I think is the objection people usually have) the rest will
follow as really natural.

You gain alot by moving away from passive filters to active. It's really a day
and night difference at times (like when the Turbosound guys didn't recognice
the sound of their own speakers, with just a very rudimentary active filter
setup).

So, no, I pass on passive filters. They are so crude approximations and is not
as easy to finetune and adapt as needed for a good summing. No, I have
basically just put them on memory lane and see no real motivation for their use
anywhere. It may seem like a harsh point of view, but I think people
overestimates the useability of passives and the cost of active filter
solutions.

Cheers,
Magnus